Why do we see winds and what causes the faster speeds
On any given day you can walk outside and feel a breeze. Whether or not that breeze is scorching hot or bitter cold all depends upon the time of the year. Going back to elementary school we learned that wind is nothing more than the movement of air, which flows from high pressure to low pressure. You can experience this by blowing air out of your mouth and by sucking liquids out of a straw. Both of those activities require pressure differences for them to occur.
The greater the pressure difference between the high and low pressure, the faster the winds will blow. You can visualize this by using a can of hairspray. If you put a little pressure on the nozzle, then just a fine mist of hairspray will come out. However, when you press harder and add more pressure on the nozzle, you see more hairspray come out of the bottle. While the atmosphere isn’t a hairspray bottle, it does paint a picture of how pressure differences impact our wind speeds.
The average wind speed in Mid-Missouri during the spring months is right around 10 mph. Of course lately this hasn’t been the case, as winds have been quite breeze with gusts as high as 30 mph. It’s these winds that have prompted heightened fire concerns and wind advisories across the region this spring.
Why though do we see winds increase during the day and decrease at night? To understand how this occurs, one must understand the basics. The higher in the atmosphere you go, the faster the wind speeds due to less friction. These winds are more pronounced during the spring months here in Missouri, due to the location of the jet stream as it begins to shift back north. As the sun rises each day it heats the earth’s surface. The heating off the earths’ surface causes the warmer air to rise, as warm air is less dense than cold air. This displaces the colder air above it and the cycle known as atmospheric mixing repeats. This mixing pulls faster air aloft down to the surface which creates the windy conditions that we experience during the afternoon hours.
The opposite occurs at night. As the sun sets, the ground cools down faster than the air aloft. This creates a warm air inversion, or a stable layer. Because the atmosphere is stable, there is no atmospheric mixing and the faster moving air is kept from mixing down to the surface.
Of course this isn’t always the case. If there is a storm or low pressure system in the area, the winds will blow day or night. Keep this in mind as we head into the coming days, with windy conditions in the forecast through at least Thursday.
Stay with ABC 17 Stormtrack as we continue to track the windy conditions and follow us on Twitter @ABC17Stormtrack.
